1. PROCESS CONTROL IN SPINNING Prof. R. Chattopadhyay IIT, Delhi

2. QUALITY ASSURANCE IN SPINNING
STEPS
Setting of Norms
Quality of incoming raw material to the Khadi Institution
Process Monitoring and Control
 Inspection of final product   

3. MATERIAL FLOW Raw cotton CENTRAL SLIVER PLANT Institutional spinning
Transportation of Sliver / roving
Khadi Institution 1
Khadi Institution2
Khadi Institution3
Internal transportation
Distributed spinning in villages
Institutional spinning
Transportation of sliver or roving
Village 1
Village 2
Village 3
Village n
Charkha 1 2 3 4 10

4. PROCESS CONTROL PROCESS Input Output Monitor Corrective action Monitor
Process parameters
/Intermediate product characteristics/Machine conditions/Work practice / process waste
Compare against norm
Compare against norm
Corrective action
Compare against norm

5. QUALITY OF INCOMING RAW MATERIAL TO CENTRAL SLIVER PLANT
Test of raw cotton in terms of physical parameters
and accept if comparable with norms
Careful transportation & storage of cotton bales
  Check sliver or roving parameters i. e
Count and count CV%
Trash % & Neps

6. Checks on material handling during packaging and
loading on trucks
- Transfer sliver into polythene bags
- Put roving bobbins into polythene bags
- Transport sliver cans, polythene bags containing sliver or roving on to the trucks.
- Properly cover sliver cans, polythene bags
containing sliver or roving on trucks

7. QUALITY OF RAW MATERIAL RECEIVED BY KHADI INSTITUTION
Checks on material handling during Unloading from
trucks
- Careful unloading of packages
- Careful internal transportation to avoid damage
- Proper storage and segregation of sliver/ roving to avoid accidental mixing
Checks on delivered sliver / roving
- Weighing of packages
- Cross checking of average count

8. DISTRIBUTUON OF ROVING OR SLIVER TO THE SPINNERS
- Ensure that the sliver or roving corresponds to the count to be spun.
–   - The package is covered in polyethylene sheet.
In - Instruction about careful handling of package during way back to village.

9. CHARKHA SPINNING GUIDELINES
Work practice related
Running of Charkha
- Run at a slow speed in the beginning and then raise speed and maintain speed at a convenient level.
- Cover the charkha once spinning is over.
  - The broken end should be pieced (joined) properly. A knot is to be avoided as it becomes too large with respect to the yarn diameter, which deteriorates fabric appearance

10. Lea Making
-All the sections of the lea should be made from same yarn count. 
-The end of the yarn should be inserted in to the inner portion of the lea.  
-Leas should be properly stored in plastic bags or fabric bags with count wise segregation by colour mark.  
-If possible, lea bundles should be segregated while storing according to the type of fibres used or count to avoid accidental mixing.

11. Maintenance related
-Follow a specified maintenance schedule in terms
of cleaning and oiling.
-Top roller pressure should be checked at regular
intervals.
-Check the condition of the aprons and driving belts (mall) and adjust if necessary.
Parameters selection
- Select parameters based on past experience that suits the raw material.

12. QUALITY ATTRIBUTES TO BE CONTROLLED IN KHADI YARN
Average Count and It’s CV%
Lea CSP
Yarn Unevenness
Imperfections
Soft and hard twisted portion
Faults
Pote
Kachara
Moore
Daghi
Bakar
Slubs
Possible reasons for deterioration in quality
Characteristics and occurrence of faults

13. PROCESS CONTROL OF CHARKHA SPUN YARN
Detection of significant shift in quality level
Investigation on the causes of departure
Taking remedial action immediately to set the process back to normal

14. Monitoring stages and Characteristics to be monitored
YARN STAGE
-Average count and count variability
-Uniformity
-Imperfections
-Count Strength Product (CSP)
INTERMEDIATE STAGES
Sliver
-Sliver count and its variability
-Sliver uniformity
-Sliver cleanliness

15. Roving
-Roving count and its variability
-Roving uniformity
-Roving cleanliness
Process Performance
      -Waste level
-End breaks in charkha
-  Productivity

16. Detection of shift in yarn count:
Example:
Nominal Count = 20 Nm
Average weight of lea = 50 gm
Count CV % = 10
S.D. of count = 5gm
Warning limit = Mean  2  S.D. = 50  10
= 60 gm and gm
Action limit = Mean  32  S.D. = 50  15
= 65gm and gm

17. Shift 65 g Lea weight ( gm) 60 g 50 g 40 g 35 g Operator ID
Lower Warning Limit (LWL)
Upper Action Limit (UAL)
Upper Warning Limit (UWL)
Lower Action Limit (LAL)
50 g
40 g
35 g
60 g
65 g
Shift

18. 65 g Lea weight ( gm) 60 g 50 g 40 g 35 g Operator ID
Lower Warning Limit (LWL)
Upper Action Limit (UAL)
Upper Warning Limit (UWL)
Lower Action Limit (LAL)
50 g
40 g
35 g
60 g
65 g

19. 65 g Lea weight ( gm) 60 g 50 g 40 g 35 g Operator ID
Lower Warning Limit (LWL)
Upper Action Limit (UAL)
Upper Warning Limit (UWL)
Lower Action Limit (LAL)
50 g
40 g
35 g
60 g
65 g

20. WHAT ACTION IS TO BE TAKEN For case I
-Wrong Draft Change Pinion ( DCP)
-Inadvertent change in draft constant
-Wrong count of sliver or roving
For case II
-Count of sliver / roving supplied is to be verified
-Too coarse and too fine sliver / roving are to be withdrawn
-Draft on charkhas are to be adjusted

21. Control of Count Variability
Operator No.
Count Values of Lea No. 1 2 3 4 5 6 7 8 9 10
Calculation of within and between count CV

22. REASONS FOR HIGH BETWEEN OPERATOR COUNT VARIABILITY (CVBO)
Difference in average hank of sliver/ roving used.
Difference in the total drafts in the charkhas
Difference in effective drafts between spindles of charkhas due to cot slippage.
Roving stretch
REASONS FOR DIFFERENCE IN AVERAGE SLIVER HANK
Difference in waste level and mechanical draft in card breaker or finisher draw frame.
DIFFERENCE IN AVERAGE ROVING HANK
Difference in sliver hank.
Draft difference in speed frames.
Differences in waste level in card.

23. DIFFERENCE IN AVERAGE DRAFT IN CHARKHAS
Wrong draft constant in charkha or wrong change pinions
Difference in effective draft within a charkha
-Slippage of top rollers, inadequate roller pressure.
ROVING STRETCHING
Inadequate roving twist, low inter fibre cohesion (specially when fibres are short),defective bobbin holder

24. YARN UNIFORMITY / UNEVENNESS
1. A routine check on all the samples received may not
be practicable.
2. Only when yarn samples for any new lot arrives , the test can be carried out by randomly selecting 30 leas from as many operators as possible.

25. REASONS FOR UNEVEN YARN
Incorrect setting of break draft on D/F, S/F or charkha.
Inadequate top roller pressure.
Wear/damaged apron or cots.
Eccentric top roller y in charkha.
High short fiber percentage in sliver or roving.
Too wide setting in the front zone of charkha.
Slipping apron.

26. YARN APPEARANCE
Subjective assessment based on visual check of yarn boards on yarns received from operators when fresh yarn lots are received from them for a new mixing .
Maintain a record according to operator ID
REASON FOR POOR APPEARANCE
High yarn unevenness
Many excessively severe thick, thin places and neps in the yarn
Presence of too many impurities like seed coat, leaves, stalks etc in the yarn

27. CORRECTIVE ACTIONS TO BE TAKEN
Check the overall condition of the charkha and roller setting
Replacement of defective drafting rollers or aprons
Cleaning of accumulation of stray fibres on drafting elements, ring, travelers, gears etc should be avoided.
Roller slippage because of low pressure or presence of oil on roller surface is to be avoided.
 Neps in sliver to be maintained as per the norms
 Cleanliness of the sliver

28. Yarn Count Strength Product (CSP)
Average CSP = 1000 for count 24 – 36 Nm
CSP CV% = 12, CSP S.D. = 120
UAL = 120 = 1360
UWL= 120 = 1240
LAL =  120 = 640
LWL= 120 = 760
Operator ID
LWL
UAL
UWL
LAL
1000
640
760 gm
1240
1360
Lea weight (g)

29. Action to be taken
Case I: Points fall below the lower Action Limit or continues to fall in between Warning and Action Limit for many operators.
 Case II: Points are distributed with a wide scatter.
Case I: A repeat check on the yarn supplied by the operator whose estimated CSP value fall below the action limit is to be performed. At least 6 leas are to be tested and the average is to be found out. If the average is found to be still lower, then remedial measures should be taken.

30. POSSIBLE REASONS FOR LOW AVERAGE CSP
-Inadequate twist in the yarn.
-Finer yarn count.
-Weak fibres in mixing.
Twist and count testing of the same are to be performed to find out whether the twist is really low or the count is fine. The lower twist could be attributed to:
Lower spindle speed due to slippage, which can be due to
Loose driving cord of spindles.
Accumulation of oil/grease on cord driving the spindles (mall).

31. Reasons for finer yarn
-Higher total draft.
-The finer sliver/roving supplied.
If count and twist are as per nominal value but CSP is still found to be less, inadvertently a sliver/ roving may have been supplied from a mixing in which the fibres are intrinsically weak.
Reasons for high strength variation
– Intermittent slippage of top roller in the charkhas.
– Variability in between yarn count produced on
different charkhas.